The present invention relates to a lactam ring-containing polymer.
N-vinylamide polymer as well as vinylamine unit-containing polymer derived therefrom through hydrolysis are considered interesting for their possible application to thermoplastic resin compatibilizing agents, dispersants, binders, thickeners and the like by making use of highly polar amino or amido group therein.
For instance, Japanese Patent Application Laying Open (Kokai) No. 57-517017 discloses that a copolymer of acrylamide, N-vinylacylamide and vinylsulfonic acid as well as its hydrolyzate have good long-term temperature stability and are suitable for petroleum tertiary recovery.
On the other hand, it is known that, during the Schmidt reaction of polyacrylic acid, according to which carboxylic groups therein are partly converted into amino groups, an amino group of a polymeric unit and an carboxylic group of a polymeric unit adjacent thereto may form a lactam ring (Journal of Polymer Science: Polymer Symposium 74, 17-30(1986)). This reaction, however, could be hardly applicable to practically produce a polymer having a high lactam ring content, since the conversion into amino groups occurs only with unsatisfactory efficiency. Furthermore, the obtained lactam ring-containing polymers are remained unknown about physical properties thereof.
Japanese Patent Application Laying Open (Kokai) No. 3-118804 shows that upon modification of a copolymer of N-vinylacetamide and acrylonitrile, a lactam ring may be formed through a reaction between an amino group derived from the vinylacetamide and an amido group in acrylamide derived from the acrylonitrile. According to the Examples of this patent application, lactam ring-containing structural units are as low as at most 8 molar % in the polymer, and there is no disclosure of a polymer having a high lactam ring content, nor any mention of advantageous effects on the physical properties offered by a lactam ring-containing structural unit.
The primary object of the present invention is therefore to provide a polymer which contains polar groups such as amido and amino groups and which exhibits good physical properties including thermal stability.